This study represents an attempt toelucidate the structural and biochemical components involved in the final phases of secretion incluuing membrane fusion and release of produt. In the ciliated protozoa, Paramecium and Tetrahymena, our previous data indicate that the presence of a specific intramembrane particle array--the fusion rosette--is correlated with the site of secretory release (Satir, B. et al., df19730 Satir, B. 1974a). From studies on a unique series of secretory mutants of Paramecium tetraurelia, we have shown that the rosette is an essential feature of the process of exocytosis in these systems. We are continuing to study the molecular events at the membrane level and govern the secretory process. Utilizing the secretory mutants of Paramecium, we will study the composition of the rosettes. We plan to analyze differences in SDS acrylamide gel pattterns of pellicles from strains with the rosettes vs. without the rosettes. Using the well define Tetrahymena system, we will attempt to develop an in vitro system of secretion. The ionic conditions necessary fo secretion, i.e., stimulus-secretion coupling, will be examined in both protozoa using Ca2 plus ionophores. These findings will be extended to higher systems, such as the mast cell which we are examining in parallel to the protozoa systems.